Tube and header-plate assembly for heat-exchange units



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ummm l man R AO EF B U T Nov.' 22, 1949 Patented Nov. 1949 TUBE ANDHEADER-PLATE ASSEMBLY FOB HEAT-EXCHAN GE UNITS Donald A. Hisey, Racine,Wis., assignor to Young Radiator Company, Racine, Wis., a corporation ofWisconsin Application February 28, 1946, Serial No. 650,795

s claims.

This invention relates to tube and header-l plate assemblies for heatexchange units, particularly ofthe type wherein a plurality of flat thinmetal tubes, supporting a series of-closelyspaced parallelheat-dispersing 1in plates, span a pair of spaced header-plates and havetheir ends inserted in openings therein and subsequently solder-sealedto said plates.

In constructions of this kind, thin sheets of metal are doubled over andwelded or brazed along an interlocking seam so as to form at tubes ofelongated cross section the sides of which are parallel and the lateraledges of which are rounded. A battery of these tubes are insertedtransversely through a series of perforated parallel sheets Iof eventhinner metal, usually called finsf which serve to disperse or dissipatethe heat from the fluid flowing through the tubes. Such a battery' ofiinned" tubes are arranged between a pair of spaced header-plates withthe tube ends inserted through openings in and solder-sealed to theheader-plates.

The openings in the header-plates are stamped out. 'I'he metal thusextruded is split and turned toform a ange around the -perimeter of eachopening. The practice heretofore has been to have the size and shape ofthe openings conform more or less exactly with the interiorcross-sectional contour of the tubes. As a consequence, the exteriortube peripheries have not always fit snugly against the openingperimeters. Moreover, the flat parallel parts of the tube at timesbecame pressed inwardly. In either 4case there was likely to be morethan the desired space between the tube sides and the perimetricalportions of the openings in the tube-p1ates-and the anges therefor.Solder being used to seal the tubes to the header-plates, and solder,not having a very great tensile strength, often proved incapable ofholding the two pieces of metal together as desired, when the heatexchange unit was subject to excessive strains incidentto the useofthese units, especially onautomotive equip-y ment.

The main objects of this invention, therefore, are to provide animproved tube and header-platel assembly for heat exchange units whereina tube end, when inserted into the anged header-plate opening, is forcedto haveI a materially greater proportion of the external periphery ofthe tube in rm contact with the perimetrical surface of the flangedheader-opening; and to provide an improved form of flanged opening inthe header. plate which, upon the insertion of a tube into an openingwill cause the sides of the tube to bow outwardly to increase theexterior peripheral contact of the tube with the perimetrical surface ofthe flanged header-plate opening.

A preferred embodimentof this invention is shown in the accompanyingdrawings, in which:

Fig. 1 is a perspective view of a section'of a heat-exchange unitembodying this invention;

Fig. 2 is an enlarged fragmentary perspective view of one end of one ofthe header-plates shown in Fig. .1;

Fig. 3 is a further enlarged fragment of the header-plate showing theshape and size of one of vthe flanged openings formed therein;

Fig. 4 is an end View of a tube, drawn to the same scale as the openingshown in Fig. 3;

Fig. 5 is a cross-sectional detail ofthe fragment shown in Fig. 3 withthe tube end positioned preparatory to being forced into the headeropenins;

Fig. 6y is a plan view of the parts as shown in Fig. 5:

Fig. '7 is an enlarged cross-sectional view,- taken vertically throughthe tube and transversely through the header-plataon the line 'l-I ofFig. `1, showing how the solder seals the tube to the header-plate;

Fig. 8 is a transverse sectional view of the same taken on the line 8-8of Fig. 7.

Heat-exchange units, of the type wherein this invention may be readilyincorporated, comprise a plurality of tubes 8 inserted through a seriesof thin, perforated heat-dispersion plates 9 and -spanning the distancebetween a pair of spaced header-plates I0 and IIA in which have beenpunched a series -of openings I 3 adapted to re# ceive the ends of thetubes 8 whereby the tubes and plates maybe solder-sealed together toform a device of the general character shown in Fig. 1.

Devices of this lkind are variously used for the transferring of heatfrom a fluid of one temperature flowing through the tubes 8 to anotherfluid of a different temperaturel flowing around. the tubes in thespaces between the heat-dispersion plates 9. To that end theheader-plates I0 and I i are connected to headers (not shown) which haveY conduits connected therewith to convey the uid of the one temperatureto and from said headers for transmission through said tubes 8. Thefluid of the other temperature is generally air forced through thespaces between the "fins and around the tubes 8.

The tubes l generally are each formed from a thin sheet metal stripdoubled upon itself and soldered along an interlocking seam I2, as shownin Figs. 4 and 5. The tubes are accordingly of elongated form, as shownin the drawings, the sides being very closely if not precisely parallel,and with the lateral edges of the tube rounded, as clearly shown inFigs. 4 and 5.

Header-plates Il and Il, involving this invention, have openings I 3punched therein. The metal extruded, in order to form the openings isslit and upset transversely of the plate to form flanges I I around theperimeters of the openings allel sides of the tubes 8. Moreover. themetal at the ends of the opening I3 is rounded as shown at I3a so as toform cam-like surfaces to the tube end.

By reason of this difference in the dimensions of the tubes 8 and theheader-plate openings I3, the tubes 8 have to be forced into theopenings I3. Such forcing of the tube ends into the open-A ings I3slightly foreshortens the longitudinal cross-sectional dimension of thetube and causes the otherwise parallel sides of the tubes 8 to be bowedoutwardly against the faces of the flanges I4 and the peripheral part ofthe openings, causing tension o'f tube wall to header opening. Thismaterially increases the probabilities of a close contact between theseperipheral surfaces, and completely obviates the necessity of openingtubes as so often has to be done with former designs. This is a veryimportant and vital factor in such tube and header-plate assemblies,since it is necessary to seal the tubes and plates at these points ofcontact. The most practical sealing medium is solder. This, of course,has to be applied in a molten state.

The sealing of these joints with molten solder can be accomplished byeither of two practical methods; melting a solder foil laid on theheader.

plates around the tubes; or dipping the headerplates, with the tubes inplace, in a solder bath.

The first of these methods involves laying a solder foil on the insideface of the header-plates before the tubes are inserted The foil isperforated to provide openingsslightly larger than but registering withthe openings I3 in the header-plates. After the tubes are inserted in afoil-covered header-plate th foil is melted by means of a ame applied bya torch, as is wellknown in the manufacture of heat-exchange units ofthis kind. The molten solder naturally spreads over the surface of theplate, and, because of the curved perimeters of the openings I3, runsinto contact with the exterior surfaces o the tubes 8. The other methodinvolves dipping the headerplates, one at a time, in a solder bath to adepth suiiicient vto not only immerse the protruding ends of the tubesbut the anges l4.\

In the first of these methods the capillarity of the opposed exteriorfaces of the tubes l and the flanges Il and the perimetrlcal areas ofthe openings I3, plus the force of gravity, will cause the molten solderto run down the tubes beyond the edges of the flanges Il. as indicatedin Fig. 7. In the second of these methods the capillarity of theseabutting surfaces causes the molten solder to be drawn up along thetubes to the opposite face of the header-plate. In either case the tubes:lare firmly sealed to the header-plates I 0 and It will be readilyunderstood that the capillarity of these abutting mbe and header-platesurfaces will be increased in proportion to the reduction in spacebetween them. Not only will the closer spacing of these peripheriesenhance the capillary action on the molten solder, but it will make fora stronger union of these surfaces than is possible where the peripheryof the tube is not forced so firmly into contact with the headerplateopening and flange. Therefore, there is less likelihood for the jointsin this structure to become weakened or broken when the heat-exchangeunit is subject to the strains of normal use, particularly on automotiveequipment.

It is va general practice in producing heat-exchange units of this kindto have the tubes 8 coated with a thin film of solder prior to the tubesbeing inserted through the fin-plates 9. After the assembly of thefin-plates 9 on the tubes, and prior to the header-plates I0 and Ilbeing pressed over the ends of the tubes, the assembled tubes andfin-plates are placed in an oven at a temperature of around 606 F. Thiscauses the film of solder on the exterior surface of the tube to meltand effect a sealed union between the tubes and the perimetrical flangesaround the openings in said fin-plates.

Other varitatlons and modications in the details of structure andarrangement of the parts may be resorted to within the spirit andcoverage of the appended claims.

I claim:

l. A tube and header plate assembly for heat exchange units comprising aplurality ofyparallel tubes of thin sheet metal of fiat elongated crosssection having substantially parallel opposite walls and rounded cornersinterconnecting the same, a plurality of longitudinally spacedmultiapertured fins disposed on and maintaining said tubes in apredetermined relationship with the tubes disposed through the aperturesin the fins and a header plate having a plurality of elliptical openingstherein corresponding in number and disposition to the number anddisposition of said tubes with the major axes of said openings beingslightly less than the major axes of said tubes and the minor axes ofsaid openings being greater than the minor axes of said tubes, the endsof the tubes being disposed within the openings with the opposite wallsadjacent thereto being bowed outwardly in substantial flush contact withthe perimetrical edges of the respective openings, whereby the ends ofthe tubes only conform to the shape of the openings and which ends haveslightly less cross sectional area. than said openings permitting saidflush contact.

2. A tube and header plate assembly as defined in and by claim 1 andincluding means permanently bonding the fins to the tubes and the tubeends to the header plate.

3. A tube and header plate assembly as defined rinandbyelaimhin s lwhich the transverse eros sectional shape of the perimetrical edges ofthe openings in the header plate is arcuate.

4. A tube and header plate assembly for heatl 'exchange units includingat least one tube of thin sheet metal of ilat elongated cross sectionhaving substantially parallel .opposite walls and rounded cornersinterconnecting the same, and a short header plate having at least oneelliptical opening therein having a major axis slightly less than themajor axis of said tube and the minor axis of said opening being greaterthan the minor A axisof said tube, the end of the tube being disposedwithin the opening with the said opposite walls adjacent thereto beingbowed outwardly in l substantial flush contact with the perimetrical ammin and-by' claim 4, in which the transverse cross sectional shape of theperimetrical edge of the opening in the header plate is arcuate.

6. A tube and header plate assembly asde'ned in and by claim 4,'andincluding means .parmanentlyV bonding the end of the tube to the plate.'A'

-A DONALD A. HISE'Y. 3

REFERENCES crrEn The following references are of record in the ille ofpatent:

Y' STATES PATENTS Name i Number 4 y Dette` l 13781243 Sonneborn Sept'.10, 1918 1,429,878'v Spery --'June`27.-1922 1,760,505l 1. .Lea .-xMay27, 1930 1,856,618 Y Brown May`3. 1932 317,572 v Whitt et al Apr. 27,i943 C ertiicate of Correction Patent No. 2,488,627 November 22, 1949.Y'

DONALD A.4 HISEY It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows:

Column 1, line 28, for the word interior read exterior;

and that the seid Letters Patent should be read With this correctiontherein that the same meV conform to the record of the case in thePatent OIce.

Signed and sealed this 11th day of April, A. D. 1950.

THOMAS F. MURPHY,

